I suppose Ten Hag should have learnt from his experience with Manchester United for him to accept to take a job for a team that management has no intentions of equipping the team for him. Perhaps that could have been what Xabi Alonso foresaw that made him accepted Real Madrid offer. How do a club sell out their key players and ain't replacing them to ensure the team make a good performance in the coming season?
I doubt that Bayern Leverkusen will sell their key players or not find replacements if Xabi Alonso was still the coach. The club started respecting Xabi Alonso after he flawlessly won the Bundesliga so if he had in mind to continue with the club, they would have listened to any decision he chooses for the team. I don't know how Eric Ten Hag will survive with the current squad of Bayern Leverkusen, but it wouldn't be easy for him and if he doesn't perform as expected he should not be blamed because we all have already seen that the team lack quality players right now, even the most experienced coach can still find it difficult to manage such a team. Besides when an experienced coach wants to go to a new team, he signs players he likes to join him over there just to increase his chances of being successful, but Eric Ten Hag moved in without the team given him that privilege of getting any player he wants.